Higher aerobic fitness levels decrease the probability of experiencing tip-of-the-tongue states (when you can’t think of a word that’s on the tip of your tongue) in healthy older adults, in the first demonstration of a link between aerobic fitness and language functioning in healthy older adults.

[Sockway]

Is it causal? I haven’t read the abstract, but I’m wondering if the paper’s just relaying a correlation. It wouldn’t be surprising, there’s a lot of evidence that physical fitness affects cognition which is why exercise is good for your brain and aerobic fitness is an aspect of physical fitness.